This invention relates generally to computer storage device configuration, and more particularly to providing persistent names to logical volumes mounted in a computer system.
Most operating systems associate a logical unit of mass storage with a device name, such as a physical hierarchical name ( device harddisk0 partition1 ), and a user-friendly name, such as a drive letter, so that the data on the storage device can be easily accessible by the higher layers of the operating system and user applications. The higher layers of the operating system and user applications assume that the user-friendly names are persistent across boot sessions. In actuality, the names are persistent only as long as the physical configuration of the computer does not change. Persistence cannot be guaranteed because such operating systems assign the user-friendly names in the order in which the storage devices are detected when booting. When the physical locations of the storage devices change, these operating systems will assign the user-friendly names to different devices. Therefore, the consistency of name assignments across multiple boot sessions is not preserved under all circumstances, and the higher operating system layers and user applications will be unable to access the data on the devices without modification.
Furthermore, most operation systems support a fixed number of user-friendly names so the number of logical units addressable through user-friendly names is limited.
Therefore, there is a need in the art for an operating system that provides persistent user-friendly names despite physical configuration changes and extends the number of user-friendly names.
The above-mentioned shortcomings, disadvantages and problems are addressed by the present invention, which will be understood by reading and studying the following specification.
Unique volume identifiers for logical volumes are used to associate logical volumes created from compute system storage devices with persistent xe2x80x9credirectedxe2x80x9d user-friendly mount names and optional drive letters which are used by higher layers of the operating system and user applications. Information regarding the redirected names is stored a persistent data structure based on the unique volume identifier. There is an entry in the data structure containing the mount name and the unique volume identifier for a logical volume so that the mount name persists across boot sessions. If the logical volume is assigned a drive letter, there is a similar entry for the drive letter that also contains the unique volume identifier. Because the operating system addresses a logical volume through a non-persistent device name, symbolic links are created between the device name and the mount name, and any optional drive letter, when the logical volume is first identified during a boot session so that the higher layers of the operating system and user applications can access the logical volume through the persistent mount name and/or drive letter.
When the physical configuration of the computer changes, the device name changes but the unique volume identifier does not. The unique volume identifier is used to locate the appropriate mount name and/or drive letter in its data structure and a new symbolic link is created with the new device name so that the symbolic link resolves the mount name and/or drive letter to the correct logical volume under all circumstances.
Because the logical volume is identified through its unique volume identifier and is not reliant on the devices being located in any particular order in the system, or being discovered in any particular order during the boot process, or being present only during the boot process, changes in the physical configuration of the computer between boots, or during a boot session, have no effect on the higher layers of the operating system and user applications which rely on the redirected name. Thus, the level of indirection provided by the invention guarantees that the higher layers of the operating system and user applications will be able to access data on a logical volume for the life of the logical volume without modifications. Furthermore, because the logical volume is always accessible through its mount name, the invention extends the finite set of drive letters commonly available in operating systems.
In one aspect of the invention, a data structure is described that contains the unique volume identifiers and the persistent redirected names. In another aspect of the invention, a mount manager is described that creates and maintains the data structure.
The present application describes computer systems, methods, and computer-readable media of varying scope. The mount manager is variously described as causing the processor of a computer to perform certain actions, as a series of steps executed from a computer-readable medium, and in terms of its interaction with objects and other system components in an object-based operating system. However, the invention is equally applicable in environments which provide for associating the unique volume identifiers, the persistent names, and the logical volume without requiring a separate mount manager or the particular data structures described in the present application. In addition to the aspects and advantages of the present invention described in this summary, further aspects and advantages of the invention will become apparent by reference to the drawings and by reading the detailed description that follows.